In power electronics, for example electric motor drives, it is known that there is a spectrum of radio frequency currents flowing from the drive as a result of circuit operation with high voltages and currents. These are known as conducted emissions and are typically measured in the range of 0.15 to 30 MHz. They emanate principally from the switched rectified DC power driving the motor. Suppression of these emissions is very important. For example, the power cables to the motor are shielded to avoid interference with operation of nearby equipment. It is also known to suppress such emissions from the upstream power electronics by installing a capacitor to earth the high frequency emissions. However, both the inherent capacitance of the power lines in the installed capacitance gives rise to resonance and, therefore, peaks in emissions that are particularly acute. In theory it is possible to damp these by installing a resistance in the power line. However, this proves to be impracticable particularly for installations with long runs of power cabling to the motor, as the resistance would have to be very highly rated to handle the expected power dissipation and avoid the risk of fire. In addition, deciding on the size and rating of such a resistor would, in large part, be dependent on the length of the cable run from the power electronics to the motor. As this is application specific, it is not a remedy that can be effected during manufacture of the drive unless the individual installation details for the motor are known.